The photo was taken at a depth of 50 cm in the Rio Atabappo in Colombia, which forms part of the border with Venezuela. What made it special was the water temperature of 32.7 °C! It was the highest water temperature we have ever measured in natural waters containing fish in South America on our JBL expeditions. But the photo contains even more interesting information for us aquarists: That the angelfish share their habitat with flag cichlids (Mesonauta festivus). The plants in the picture are not underwater plants. In Rio Atabappo there are no aquatic plants under water at all. If you find anything green under water it’s leafy broken-off branches, or overwater plants forced to survive under water for a while due to a high water level. The water colour shows the typical blackwater of the region with no measurable general or carbonate hardness, a conductivity of 19 µS/cm and a strongly acidic pH.
Just how dangerous are crocodiles for snorkelers?
While snorkeling in our ornamental fish habitats, we may encounter crocodiles. In South America, this is 99.9% unproblematic, as they are harmless caimans that are more afraid of us than we are of them. Only the black caiman can be really dangerous, but that's exactly why they have been practically wiped out.
In Australia, the situation is different. Two types of crocodiles live there: The freshwater forms, called freshies, and the saltwater crocodiles, called salties. The freshies are usually harmless and when encountered they retreat or threaten by opening their mouths. If you then make an orderly retreat you’ll be able to leave the water with all your limbs intact. This is not the case with salties. Even their maximum size of about five meters is impressive. Waters where saltwater crocodiles live are marked with warning signs in three languages. Fatal is the fact that these lizard-like reptiles can be encountered hundreds of kilometers inland from Darwin on the north coast! At high tide, they advance far inland in the rivers and then, as the water level recedes, find themselves in pools where they really have no business being. And when they are hungry too...
Find out more about Colombia here: Wyprawa badawcza 2022 Kolumbia I
